“It’s probably too expensive to keep a group of thugs handy to take care of biz as these little vandals exit, but having entrance doors that lock down to prevent entry by a suddenly assembling group of hoods wouldn’t be that bad.”
Never happen.
Building and fire code regulations...
My local bank near the mall has airlock-type doors. Outer door opens to short corridor. Inner door will only open if outer door is closed, and presumably if a teller hits the panic button anybody in the airlock will be trapped there.